Method of making a read head with improved lead layers at an air bearing surface

ABSTRACT

The high resistance lead layers of a read head extend straight back into the head from each of the first and second edges of the read sensor. This lessens the length of each of the high resistance lead layers so that they do not have to be made thicker to satisfy resistance requirements. Accordingly, a lateral width of each high resistance lead portion along the ABS and a thickness thereof are chosen so as to minimize the thickness while yet satisfying the resistance requirements. Further, a method of making the first and second lead layers is provided that minimizes the thickness of the high resistance lead layers. Instead of constructing the high resistance lead layers first, the present method constructs the high resistance lead layers last so that the high resistance lead layers are not altered by subsequent processing steps.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a read head with improved lead layersat an air bearing surface and more particularly to high resistance leadlayer portions of first and second lead layers that have improveddimensions and performance.

2. Description of the Related Art

The heart of a computer is an assembly that is referred to as a magneticdisk drive. The magnetic disk drive includes a rotating magnetic disk,write and read heads that are suspended by a suspension arm above therotating disk and an actuator that swings the suspension arm to placethe read and write heads over selected circular tracks on the rotatingdisk. The read and write heads are directly mounted on a slider that hasan air bearing surface (ABS). The suspension arm biases the slider intocontact with the surface of the disk when the disk is not rotating but,when the disk rotates, air is swirled by the rotating disk adjacent theABS to cause the slider to ride on an air bearing a slight distance fromthe surface of the rotating disk. The write and read heads are employedfor writing magnetic impressions to and reading magnetic impressionsfrom the rotating disk. The read and write heads are connected toprocessing circuitry that operates according to a computer program toimplement the writing and reading functions.

The write head includes a coil layer embedded in first, second and thirdinsulation layers (insulation stack), the insulation stack beingsandwiched between first and second pole piece layers. A magnetic gap isformed between the first and second pole piece layers by a write gaplayer at an air bearing surface (ABS) of the write head. The pole piecelayers are connected at a back gap. Current conducted to the coil layerinduces a magnetic field across the gap between the pole pieces. Thisfield fringes across the gap at the ABS for the purpose of writinginformation in tracks on moving media, such as in circular tracks on arotating disk.

The read head includes first and second shield layers, first and secondgap layers, a read sensor and first and second lead layers that areconnected to the read sensor. The first and second gap layers arelocated between the first and second shield layers and the read sensorand the first and second lead layers are located between the first andsecond gap layers. The distance between the first and second shieldlayers determines the linear read density of the read head. Accordingly,the first and second gap layers are constructed as thin as possiblewithout shorting the lead layers to the first and second lead layers.High linear density results in more bits being read by the read head perlength of magnetic track passing by the read head on the rotating disk.

Each of the first and second leads has a high resistance lead layer anda low resistance lead layer. Each high resistance lead layer is amaterial that is resistant to corrosion since it has an edge exposed atthe air bearing surface. The high resistance lead layer typicallyincludes a film made of tantalum (Ta). Each low resistance lead layer iscorrosive, but this is of no consequence since it is protected from theoutside environment by being recessed in the head. The low resistancelead layer typically includes a film made of copper (Cu) or gold (Au).

The high resistance layer has multiple films. One of the films is the Tafilm for conducting a sense current through the read sensor. Another oneof the films is a hard bias film for longitudinally biasing the readsensor so that it is magnetically stabilized to prevent Barkhousennoise. In the past each high resistance lead layer extended from arespective side edge of the read sensor in a lateral direction (parallelto the ABS) before it extended back into the head to make contact withthe low resistance lead layer. The longer the extension of the highresistance lead layer the thicker the high resistance lead layer has tobe in order to maintain its resistance at an acceptable level. When theresistance gets too high the read head is damaged by heat. When theextension of the high resistance lead layer is made thicker in order tokeep its resistance down planarization between the top surfaces of theread sensor layer and the high resistance lead layers is degraded.

The read sensor is bounded by a front edge at the ABS, first and secondside edges that extend perpendicular to the ABS and a back edge that isspaced from the ABS and that defines a stripe height of the read head.Each high resistance lead layer has a forward edge that makes contactwith a respective one of the first and second edges of the read sensor.This type of connection is referred to in the art as a contiguousjunction. When the high resistance lead layers are thickened in order toreduce resistance their top surfaces are elevated with respect to thetop surface of the read sensor. This causes a step adjacent each sideedge of the read sensor. Unfortunately, these steps are replicatedthrough the second gap layer and the second shield/first pole piecelayer all the way to the write gap layer of the write head. Since thewrite head has to be made wider than the read head the write gapreplicates these steps and takes on a curvature that seriously affectsthe write capability of the write head. The curved write gap causes thewrite head to write curved bits (magnetic signals) on the rotatingtrack. When the straight across read head reads these curved bits itprogressively loses magnetic intensity from a center of the bit towardouter edges of the track. Accordingly, there is a strong felt need topromote planarization of the read sensor and the high resistance leadsso as to reduce write gap curvature.

We sought a method to construct the lead layers that would promoteplanarization between the read sensor and the high resistance leadlayers at the ABS. One method investigated constructs the highresistance lead layers before the low resistance lead layers. In thismethod a read sensor material layer is deposited over an entire wafer. Afirst mask is formed that has openings at the high resistance lead layersites which extend to the first and second side edges of the readsensor. Read sensor material is milled out at the high resistance leadlayer sites and the high resistance lead layer material is deposited toform first and second high resistance lead layers at the high resistancelead layer sites that make contiguous junctions with the first andsecond side edges of the read sensor. This establishes the track widthof the read. Track width density (number of tracks per inch of themagnetic disk) times the aforementioned linear density is the arealdensity of the read head. Increasing the areal density increases the bitdensity (number of bits per square inch of the magnetic medium) of thedisk drive. The first mask is removed and a second mask is formed thatcovers the read sensor and the high resistance lead layers. All exposedread sensor material is then milled away to define the back edge andstripe height of the read sensor. The stripe height is important inestablishing the magnetics of the read sensor. The second mask is thenremoved and a third mask is formed that has openings at low resistancelead layer sites. Low resistance lead layer material is then depositedthat forms first and second low resistance lead layers that overlap andengage the first and second high resistance lead layers. The third maskis then removed.

Unfortunately, the aforementioned method of making subjects the highresistance lead layers to subsequent processing since they areconstructed before defining the stripe height of the read sensor andbefore constructing the low resistance lead layers. Since the secondmask must be slightly inboard of the outer edges of the high resistancelayer in order to ensure complete removal of unwanted read sensormaterial an outer edge portion of each high resistance lead layer issubjected to milling. Reduction of the high resistance layers due tosubsequent processing requires that the thickness of the high resistancelayers be increased as deposited in order to satisfy the resistancerequirements. As stated hereinabove, thicker high resistance leadsresults in increased write gap curvature. Accordingly, there is a strongfelt need to provide a method of making the read sensor leads that willnot contribute to thicker high resistance lead layers.

SUMMARY OF THE INVENTION

Instead of extending the high resistance lead layers laterally beforemaking a turn to connect to the low resistance lead layers the presentinvention extends the high resistance lead layers straight back into thehead from each of the first and second side edges of the read sensor.This lessens the length of the each of the high resistance lead layersso that they do not have to be made thicker to satisfy the resistancerequirements. Accordingly, a lateral width of each high resistance leadportion along the ABS and a thickness thereof are chosen so as tominimize the thickness while satisfying the resistance requirements.

Further, a method of making the first and second lead layers is providedthat minimizes the thickness of the high resistance lead layers. Insteadof constructing the high resistance lead layers first, the presentmethod constructs the high resistance lead layers last. After depositingread sensor material over a wafer a first mask is formed that hasopenings at the low resistance lead layer sites. After milling the readsensor material from the low resistance lead layer sites low resistancelead layer material is deposited. This forms the first and second lowresistance lead layers. A second mask is then formed that covers theread sensor site and the low resistance lead layers. The second mask hasa large opening that exposes all unwanted read sensor material and hasan edge that is located at the desired back edge (stripe height) of theread sensor. The read sensor material is milled away and the second maskis removed leaving the read sensor with a desired stripe height. Next,the third mask is formed with openings at the first and second highresistance lead layer sites. After removing read sensor material at thefirst and second high resistance lead layer site high resistance leadlayer material is deposited to form the first and second high resistancelead layers. The third mask is then removed. The high resistance leadlayers are now complete and are more predictable since they have notbeen subjected to processing steps in the construction of the lowresistance lead layers and the read sensor.

The present invention provides a special step after forming the secondmask and milling away the unwanted read sensor material. The second maskcovers the read sensor site as well as a portion of read sensor materiallayer adjacent first and second edge sites of the read sensor site. Thesecond mask cannot define the first and second edges of the read sensorsince this is the function of the third mask which implements acontiguous junction between the high resistance lead layers and the sideedges of the read sensor. Accordingly, the second mask leaves someunwanted read sensor material adjacent each edge of the read sensorsite. When the third mask is formed the openings therein expose thisunwanted read sensor material as well as a portion of the first gaplayer where unwanted read sensor material was removed during the secondmasking step. It should be noted that if each opening in the third maskdid not expose some of the first gap layer there would be no assurancethat all read sensor material was removed except at the read sensorsite. Without protection the first gap layer is exposed to a developerfor patterning the third mask and an ion milling process afterpatterning the third mask. The developer and the ion milling willseriously damage the insulating quality of the first gap layer. Thisproblem has been overcome in the present invention by depositing aninsulation refill material after milling has occurred in the secondmasking step. The insulation refill material will now be adjacent theunwanted read sensor material in each opening of the third mask.Accordingly, when milling is implemented the milling mills insulationrefill material as well as the read sensor material. In the preferredembodiment the thickness of the refill insulation material is designedso that the refill insulation material and the read sensor material areconsumed at the same time in each of the openings of the third mask atthe high resistance lead layer sites. This then exposes the first gaplayer with no damage. The high resistance lead layer material can thenbe deposited in the openings in the third mask. The third mask is thenremoved.

An object of the present invention is to provide a read head withimproved high resistance lead layers at the ABS.

Another object is to provide a minimal extension of the high resistancelead layers of a read head so that their thickness does not have to beincreased to satisfy resistance requirements.

A further object is to provide a read head with first and second leadlayers that are more planarized with respect to a read sensor.

Still another object is to provide a read head that does not adverselyimpact the straightness of a write gap layer of a write head.

Still another object is to provide a method of making first and secondlead layers of a read head that promotes planarization of the leadlayers and a read sensor.

Still other objects and advantages of the invention will become apparentupon reading the following description taken together with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an exemplary magnetic disk drive;

FIG. 2 is a view taken along plane 2--2 of FIG. 1 showing a slider witha magnetic head (hidden lines) of the disk drive;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisk and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is an ABS view of the magnetic head taken along plane 5--5 ofFIG. 2;

FIG. 6 is a partial view of the slider and a magnetic head as seen inplane 6--6 of FIG. 2;

FIG. 7 is a partial ABS view of the slider taken along plane 7--7 ofFIG. 6 to show the read and write elements of the magnetic head;

FIG. 8 is view taken along plane 8--8 of FIG. 6 with all material abovethe coil layer and lead layers removed;

FIG. 9 is a plan view of a prior art read sensor and first and secondleads connected thereto;

FIG. 10 is a view taken along plane 10--10 of FIG. 9;

FIG. 11 is a plan view of the present read sensor and first and secondleads of the present invention;

FIG. 12 is a view taken along plane 12--12 of FIG. 11;

FIG. 13 is a plan view of a portion of a wafer wherein a layer of spinvalve material has been deposited and wherein read sensor and first andsecond lead layer sites are shown in phantom;

FIG. 14 is a view taken along plane 14--14 of FIG. 13;

FIG. 15 is a view taken along plane 15--15 of FIG. 13;

FIG. 16 is the same as FIG. 13 except a first mask has been formed withopenings where SV material has been milled and high resistance leadlayer material has been deposited;

FIG. 17 is a view taken along plane 17--17 of FIG. 16;

FIG. 18 is a view taken along plane 18--18 of FIG. 16;

FIG. 19 is the same as FIG. 16 except the first mask has been removedand a second mask has been formed wherein the read sensor has beendefined by milling

FIG. 20 is a view taken along plane 20--20 of FIG. 19;

FIG. 21 is a view taken along plane 21--21 of FIG. 19;

FIG. 22 is the same as FIG. 19 except the second mask has been removedand a third mask has been formed after which low resistance lead layermaterial has been deposited;

FIG. 23 is a view taken along plane 23--23 of FIG. 22;

FIG. 24 is a view taken along plane 24--24 of FIG. 22;

FIG. 25 is the same as FIG. 22 except a second gap layer has beendeposited;

FIG. 26 is a view taken along plane 26--26 of FIG. 25;

FIG. 27 is a view taken along plane 27--27 of FIG. 25;

FIG. 28 is a view taken along plane 28--28 of FIG. 25;

FIG. 29 is a plan view of a portion of a wafer wherein spin valvematerial has been deposited as a first step in implementing the methodof the present invention;

FIG. 30 is the same as FIG. 29 except a first mask has been formed withfirst and second openings at low resistance lead layer sites;

FIG. 31 is the same as FIG. 30 except ion milling has been implementedto remove the spin valve material within the first and second openings;

FIG. 32 is the same as FIG. 31 except low resistance lead layer materialhas been deposited in the first and second openings;

FIG. 33 is the same as FIG. 32 except the first mask has been removedleaving first and second low resistance lead layers;

FIG. 34 is the same as FIG. 33 except a second mask has been formedcovering the first and second low resistance lead layers and a readsensor site;

FIG. 35 is the same as FIG. 34 except milling has been implemented todefine a back edge of the read sensor;

FIG. 36 is the same as FIG. 35 except a refill insulation layer has beendeposited;

FIG. 37 is the same as FIG. 36 except the second mask has been removedleaving the first and second low resistance lead layers with refillmaterial therearound;

FIG. 38 is the same as FIG. 37 except a third mask has been formed withfirst and second openings at high resistance lead layer sites;

FIG. 39 is the same as FIG. 38 except material within the openings ofthe first and second high resistance lead layer sites has been milledaway;

FIG. 40 is the same as FIG. 39 except high resistance lead layermaterial has been deposited;

FIG. 41 is the same as FIG. 40 except the third mask has been removed;

FIG. 42 is the same as FIG. 41 except the refill insulation material hasbeen removed; and

FIG. 43 is a block diagram of steps in the method for completing theconstruction of the read head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Magnetic Disk Drive

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views there is illustratedin FIGS. 1-3 a magnetic disk drive 30. The drive 30 includes a spindle32 that supports and rotates a magnetic disk 34. The spindle 32 isrotated by a motor 36 that is controlled by a motor controller 38. Acombined read and write magnetic head 40 is mounted on a slider 42 thatis supported by a suspension 44 and actuator arm 46. A plurality ofdisks, sliders and suspensions may be employed in a large capacitydirect access storage device (DASD) as shown in FIG. 3. The suspension44 and actuator arm 46 position the slider 42 so that the magnetic head40 is in a transducing relationship with a surface of the magnetic disk34. When the disk 34 is rotated by the motor 36 the slider is supportedon a thin (typically, 0.05 μm) cushion of air (air bearing) between thesurface of the disk 34 and the air bearing surface (ABS) 48. Themagnetic head 40 may then be employed for writing information in theform of magnetic field incursions or the absence thereof to multiplecircular tracks on the surface of the disk 34, as well as for readinginformation in the same form therefrom. Processing circuitry 50exchanges signals, representing such information, with the head 40,provides motor drive signals for rotating the magnetic disk 34, andprovides control signals for moving the slider to various tracks. InFIG. 4 the slider 42 is shown mounted to the suspension 44. Thecomponents described hereinabove may be mounted on a frame 54, as shownin FIG. 3.

FIG. 5 is an ABS view of the slider 42 and the magnetic head 40. Theslider has a center rail 56 that supports the magnetic head 40, and siderails 58 and 60. The rails 56, 58 and 60 extend from a cross rail 62.With respect to rotation of the magnetic disk 34, the cross rail 62 isat a leading edge 64 of the slider and the magnetic head 40 is at atrailing edge 66 of the slider.

Magnetic Merged Head

FIG. 6 is a side cross-sectional elevation view of the merged MR or spinvalve head 40 which has a write head portion 70 and a read head portion72, the read head portion employing a magnetoresistive (MR) or spinvalve sensor 74. FIG. 7 is an ABS view of FIG. 6. The sensor 74 islocated between first and second gap layers 76 and 78 and the gap layersare located between first and second shield layers 80 and 82. Inresponse to external magnetic fields, the resistance of the sensor 74changes. A sense current I_(S) conducted through the sensor causes theseresistance changes to be manifested as potential changes. Thesepotential changes are then processed as readback signals by theprocessing circuitry 50 shown in FIG. 3.

The write head portion of the merged head includes a coil layer 84located between first and second insulation layers 86 and 88. A thirdinsulation layer 90 may be employed for planarizing the head toeliminate ripples in the second insulation layer caused by the coillayer 84. The first, second and third insulation layers are referred toin the art as an "insulation stack". The coil layer 84 and the first,second and third insulation layers 86, 88 and 90 are located betweenfirst and second pole piece layers 92 and 94. The first and second polepiece layers 92 and 94 are magnetically coupled at a Aback gap 96 andhave first and second pole tips 98 and 100 which are separated by awrite gap layer 102 at the ABS. As shown in FIGS. 2 and 4, first andsecond solder connections 104 and 106 connect leads from the sensor 74to leads 112 and 114 on the suspension 44 and third and fourth solderconnections 116 and 118 connect leads 120 and 122 from the coil 84 (seeFIG. 8) to leads 124 and 126 on the suspension. A wear layer 128 may beemployed for protecting the sensitive elements of the magnetic head, asshown in FIGS. 2, 4, 6 and 7. It should be noted that the merged head 50employs a single layer 82/92 to serve a double function as a secondshield layer for the read head and as a first pole piece for the writehead. A piggyback head employs two separate layers for these functions.

Prior Art Magnetic Head

FIG. 9 shows a prior art partially completed read head which includes aspin valve (SV) sensor 132 connected at its side edges to first andsecond lead layers 134 and 136. The spin valve sensor 132 and the leadlayers 134 and 136 are on a first gap layer (G1) 138. The lead layers134 and 136 include high resistance lead layer portions (LI) 140 and142, respectively, and low resistance lead layer portions (LII) 144 and146 respectively. The low resistance lead layers 144 and 146 extend fromvia sites to front edges 147. Each of the high resistance lead layers140 and 142 extends transverse the head (parallel to the ABS), thencerearwardly to connect with the low resistance lead layer portions 144and 146. As shown, the high resistance lead layer portions 140 and 142may completely overlap the complete low resistance lead layer portions144 and 146 all the way to the via sites as desired. Because of thetransverse extension of the high resistance lead layer portions 140 and142 before they bend 90° to connect to low resistance lead layers 144and 146 they will be required to have increased thickness in order tolower their resistance to an acceptable level. This extra thicknessresults in a higher profile and write gap curvature which is explainedhereinbelow.

FIG. 10 is a view taken along plane 10--10 of FIG. 9 with the secondread gap layer (G2) 148, the second shield and first pole piece layer(S2/P1) 150, the write gap layer (G3) 152 and the second pole piecelayer (P2) 154 added thereto. It can be seen that the higher profile ofthe first and second high resistance lead layer portions 140 and 142relative to the spin valve sensor 132 causes steps that are replicatedthrough the second read gap layer 148 and the second shield first polepiece layer 150 to the write gap layer 152. This causes the write gaplayer 152 to have a curvature which will, in turn, cause the write headto write curved magnetic signatures on the circular track of therotating disk. When the straight-across spin valve sensor 132 ismandated to read this magnetic information the signal will be strong atthe center of the spin valve sensor 132 and will decay toward its edgesbecause of the curvature of the magnetic signature that it is reading.

Present Magnetic Head

In FIG. 11 the present partially completed read head 160 is illustratedwherein a spin valve sensor 162 is connected to first and second leadlayers 164 and 166. The spin valve sensor 162 and the first and secondlead layers 164 and 166 are on a first gap layer (G1) 168. The first andsecond lead layers 164 and 166 include first and second high resistancelead layer portions (LI) 170 and 172, respectively, and first and secondlow resistance lead layer portions (LII) 174 and 176, respectively. Thefirst and second high resistance lead layer portions 170 and 172 extendstraight back from the ABS instead of making a 90° bend, as shown inFIG. 9 in the prior art embodiment. With this arrangement the length ofthe high resistance lead layer portions 170 and 172 are minimized sothat their thickness can be reduced. The first and second highresistance lead layer portions 170 and 172 overlap the first and secondlow resistance lead layer portions 174 and 176 so as to make electricalconnection therewith. If desired the first and second high resistancelead layer portions 170 and 172 may completely overlap the lowresistance lead layer portions 174 and 176 instead of partiallyoverlapping them as shown in FIG. 11.

FIG. 12 is an ABS illustration of FIG. 11 with a second read gap layer(G2) 178, a second shield first pole piece (S2/P1) 180, a write gaplayer (G3) 182 and a second pole tip (P2) 184 added thereon. As statedhereinabove, since the first and second lead layer portions 170 and 172have less length than the first and second high resistance lead layerportions 140 and 142 in the prior art embodiment, shown in FIG. 9, theirthickness can be less as illustrated in FIG. 12. While no step is shownbetween the first and second high resistance lead layer portions 170 and172 relative to the spin valve sensor 162 for illustration purposes weclaim that any step therebetween will be less than the step shown inFIG. 10 for the prior art embodiment due to our invention as shown inFIG. 11.

It should be noted from FIGS. 11 and 12 that when the second gap layer(G2) 178 is formed at the locations where the high resistance leadlayers (LI) 170 and 172 overlap the low resistance lead layers (LII) 174and 176 that the first and second low resistance layers (LII) 174 and176 are sandwiched between the first gap layer 168 and a portion of thefirst and second high resistance layers (LI) 170 and 172. In a uniquemethod of manufacturing, which will be described in detail hereinafter,the first and second high resistance lead layers (L1) 170 and 172 areconstructed after the formation of the first and second low resistancelead layers (LII) 174 and 176 and after definition of the spin valvesensor 162 so that the first and second high resistance lead layers (LI)170 and 172 are not subjected to process variations which decrease andmake their final size unpredictable. When there are process variationsthe first and second high resistance lead layers (L1) 170 and 172 mustbe made thicker in order to compensate for these variations. In order toensure that proper resistance requirements are met for the sense circuitthe designers err on the side of making the first and second highresistance lead layers (L1) 170 and 172 with an extra thickness so thatafter the process variations the first and second high resistance leadlayers (L1) 170 and 172 are not below the thickness that is required tosatisfy the resistance requirements. This extra thickness to ensure theresistance requirements results in steps on each side of the spin valvesensor 162 which are replicated to the write gap layer 182 in the formof a write gap curvature. Accordingly, by constructing the first andsecond high resistance lead layers (LII) 174 and 176 and defining thespin valve sensor 162 before forming the first and second highresistance lead layers (L1) 170 and 172, write gap curvature due to anextra thickness of the first and second high resistance lead layers (LI)170 and 172 to account for process variations has been obviated.

FIGS. 13-28 illustrate a previous method of making a read head and FIGS.29-43 illustrate the present process for making the present read head.In both methods, ion beam deposition or sputter deposition is employedfor depositing the metal and insulation layers. The masks are preferablybilayer photoresist layers wherein a bottom photoresist layer isrecessed from a top photoresist layer so that a dissolvent can dissolvethe bottom layer, thereby permitting the mask to be lifted from thewafer carrying with it the sputtered material deposited thereon.Stippled layers are insulation layers and heavy lines show the outlinesof the masks. LI represents a high resistance lead layer and LIIrepresents a low resistance lead layer. S1 and S2 designate first andsecond shield layers and G1 and G2 designate first and second read gaplayers.

Exemplary Method of Construction of Prior Art Magnetic Head

FIG. 13 is a plan view of a portion 200 of a wafer where a spin valve(SV) read head is to be constructed along with other read heads (notshown) arranged in rows and columns (not shown) on the wafer. The waferportion 200 shows a read sensor site 202, first and second via sites 204and 206, and first and second lead layer sites 208 and 210 whichelectrically connect side edges of the sensor to the via sites. Each viasite 204 and 206 is a vertically disposed (out of paper) electricalconductor connecting a lead to a respective terminal (see 104 and 106 inFIG. 2). As shown in FIG. 14, a first shield layer 212, a first gaplayer 214 and a SV material layer 216 have been formed while, as shownin FIG. 15, the first shield layer 212, the first insulative gap layer214, a first insulation layer 218 and the SV material layer 216 havebeen formed. In this process, a first mask (not shown) was employed forconstructing the first insulation layer 218 on top of the first gaplayer 214 behind the sensor site along line 222. The purpose of thefirst insulation layer 218 is to provide extra insulation for the firstand second lead layers that are to be constructed at the lead layersites 208 and 210. The extra insulation prevents shorting of the leadsthrough pinholes in the first gap layer 214 to the first shield layer212. It should be noted that a front portion of each lead layer sitebelow line 222 is left unprotected by the first insulation layer 218.

In FIG. 16 a liftoff mask 224 is employed for covering the entire waferportion except portions 226 and 228 within the first and second leadlayer sites. As shown in FIGS. 17 and 18, the SV material layer 216within the front lead layer sites 226 and 228 is milled away and hardbias and first lead layer films (shown as one film 230) are deposited onthe first gap layer 214. It should be noted that the film 230 is formedas a full film deposition in which a portion of the film 230 isdeposited on top of the mask 224. As stated hereinabove, the mask 224 isa bilayer photoresist mask (shown as one layer) with the bottom layerrecessed from the top layer so that a dissolvent can dissolve thebottom. This allows the mask 224 to be removed from the wafer along withthe film 230, which is done in a subsequent step. It should be noted inFIGS. 16 and 18 that the SV sensor material 216 at the sensor site 202has been formed with a side edge 232 which directly abuts an end 234 ofthe film 230 at the first lead layer site to form a contiguous junctiontherebetween. An opposite side edge 236 of the sensor also forms acontiguous junction with an end 238 of the film 230 at the second leadlayer site 228. In FIGS. 19, 20 and 21, the mask 224 in FIG. 16 has beenremoved and a second mask 240 has been formed covering only the sensorsite 202 and slightly smaller portions of 226 and 228 of the first andsecond lead layer sites. As shown in FIGS. 20 and 21, the remainder ofthe SV material 216 is ion milled away so as to define the height of theMR sensor, which is shown at 242. Unfortunately, a portion (not shown)of the perimeter of the first lead layer film 230, is removed therebyelevating its resistance.

In FIGS. 22, 23 and 24, the second mask 240 of FIG. 19 has been removedand a third mask 244 has been formed over the entire wafer portion 200,except rear portions 246 and 248 of the first and second lead layersites. A second lead layer film 250 is deposited in the openings 246 and248 so as to overlap and make connection with the underlying first leadlayer films so that the lead layer films extend to the via sites 204 and206. In FIG. 28, a second insulation layer 256 is formed in the rearportion of the head outside of the MR sensor frame, a front boundarythereof being shown at 258 in FIG. 25. A fourth mask (not shown) isemployed for forming the second insulation layer 256. After removing thefourth mask a full film of a second insulative gap layer (G2) 260 isformed, as shown in FIGS. 25-28. It should be noted that in reality thelead layers 230 and 250 throughout the figures having sloping side edgesand the lead layer 230 will have a higher profile than the spin valvesensor 216 in FIG. 18.

Present Method of Construction

FIG. 29 shows a portion of a wafer 300 where a read head is to beconstructed. After depositing a first shield layer (S1) 302 and a firstgap layer in (G1) 304 a read sensor material layer 306 is deposited onthe wafer. In a preferred embodiment the read sensor material is a spinvalve (SV) material.

FIG. 30 is the same as FIG. 29 except a first lift off mask 308 has beenformed which has openings 310 and 312 at first and second low resistancelead layer sites. These openings are recessed from a back edge of a readsensor site which will be explained in more detail hereinafter. FIG. 31is the same as FIG. 30 except ion milling has been implemented to removeread sensor materials (SV) in the first and second low resistance leadlayer sites 310 and 312. This causes the first gap layer (G1) to beexposed at the first and second lead sites 310 and 312. FIG. 32 is thesame as FIG. 31 except low resistance lead layer material (LII) has beendeposited in the first and second lead layer sites 310 and 312. FIG. 33is the same as FIG. 32 except the first mask 308 has been removedleaving first and second low resistance lead layers 314 and 316surrounded by lead sensor material (SV).

FIG. 34 is the same as FIG. 33 except a second mask 320 has been formedwhich covers the first and second low resistance lead layers 314 and 316except for a slight peripheral edge thereof Accordingly, the mask 320 isslightly smaller than the first and second lead layers 314 and 316 sothat in a subsequent ion milling step there is assurance of completeremoval of the read sensor material (SV) therearound. The mask 320 alsocovers a read sensor site 322 with an outer edge of the mask located ata back edge site 324 of the read sensor site 322. The location of theback edge 324 is important for defining the stripe height of the sensorwhich establishes the magnetics of the read sensor in the read headcircuit. When the read sensor is lapped to the ABS, the distance betweenthe ABS and the edge 324 is the stripe height. The mask 320 furthercovers read sensor material layer portions 326 and 328 on each side ofthe read sensor site 322. This is necessary for making contiguousjunctions at first and second side edge sites 330 and 332 of the readsensor with first and second high resistance lead layers which will bedescribed in more detail hereinafter.

FIG. 35 is the same as FIG. 34 except ion milling is implemented toremove all sensor material (SV) not covered by the mask 320. This ionmilling forms the back edge 324 which is the aforementioned stripeheight of the read head. In FIG. 36 an insulation refill material isdeposited in order to protect the first gap layer, which is typicallyaluminum oxide (Al₂ O₃) from damage from a developer, typically analkaline based material, during the next (third) masking layer process.Further, the insulation refill material covers the first gap layerportions opened by the next (third mask) and is preferably a thicknessso that it will be completely consumed at the same time that unwantedread sensor material adjacent thereto is consumed. In FIG. 37 the secondmask is removed leaving read sensor material at the read sensor site 322and the adjacent read sensor material layer portions 326 and 328. Theread sensor site 322, the portions 326 and 328 and the first and secondlow resistance lead layers 314 and 316 are now surrounded by refillinsulation material.

FIG. 38 is the same as FIG. 37 except a third mask 340 has been formedwith openings 342 and 344 at first and second high resistance lead layersites. Each opening has an inside edge which is adjacent a respectiveone of the first and second side edge sites 330 and 332 of the sensor322. After ion milling, these inside edges will establish the trackwidth of the sensor site 322. The openings 342 and 344 expose unwantedread sensor material portions 326 and 328, as well as refill materiallayer portions 346 and 348 adjacent thereto. As stated hereinabove therefill material layer portions 346 and 348 were deposited to protect thevery thin first gap layer (G1) thereunder. It should be the refillmaterial layer portions 346 and 348 are selected so that they areresistant to developer (potassium hydroxide base) which is employed inremoving light exposed portions of the third mask 340. The refillmaterial layer portions 346 and 348 protect the first gap layer in (G1)from ion milling which is implemented in the next step. The refillmaterial may be C₂, SiO₂ or NiO.

In FIG. 39 the unwanted read sensor material layer portions 342 and 344and the refill material insulation layer portions 346 and 348 (see FIG.38) are milled away to expose the first gap layer (G1) within theopenings 342 and 344. It should be noted that the refill layerinsulation portions 346 and 348 protected the first gap layer (G1)during this ion milling operation. It is preferred that the type ofmaterial and thickness of the refill insulation material layer be chosenso that it is consumed simultaneously with the consumption of theunwanted read sensor material layers 326 and 328 by the ion milling inFIG. 39. This can be easily accomplished by comparing the milling ratesof the read sensor and refill material layers and then adjusting thethickness of the refill material layer accordingly. It should also benoted that had the refill material insulation layer portions 346 and348, as shown in FIG. 38, not been deposited that the ion milling inFIG. 39 would have ion milled the first gap layer (G1) at 346 and 348.

FIG. 40 is the same as FIG. 39 except high resistance lead layermaterial has been deposited in the openings of the third mask 340 toform first and second high resistance lead layers 350 and 352 whichpartially overlap the first and second low resistance lead layerportions 314 and 316 for electrical connection thereto. If desired, thehigh resistance lead layers 350 and 352 can completely overlap the lowresistance lead layers 314 and 316. In FIG. 41 the third mask 340 isremoved leaving the first and second high resistance lead layers 350 and352 and the first and second low resistance lead layers 314 and 316surrounded by refill insulation material. In FIG. 42 the refillinsulation material may be removed by a selective process, such aschemical or reactive ion etching, exposing the first gap layer (G1).Thereafter the second gap layer (G2), the second shield layer (S2) and awrite head may be formed, as shown in FIG. 43, to complete a merged headas shown in FIGS. 7 and 12.

Clearly, other embodiments and modifications of this invention willreadily occur to those of ordinary skill in the art upon reading theseteachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

We claim:
 1. A method of making a magnetic head that has an air bearingsurface (ABS) comprising:forming a first shield layer; forming a firstgap layer on the first shield layer; depositing a read sensor materiallayer on the first gap layer; removing first and second portions of theread sensor material layer at first and second lead layer sites that arerecessed from an ABS site; depositing first and second low resistancelead layers at the first and second lead layer sites; removing anadditional portion of the read sensor material layer to form a back edgeand stripe height of an MR read sensor site that is recessed from theABS site; removing further first and second portions of the read sensormaterial at first and second high resistance lead layer sites andadjacent first and second side edges of the read sensor site to define atrack width of the read head; depositing first and second highresistance lead layers at the first and second high resistance leadlayer sites that abut the first and second side edges and cover at leasta portion of the first and second low resistance lead layersrespectively; forming a second gap layer on the read sensor site and thefirst and second high and low resistance lead layers; and forming asecond shield layer on the second gap layer.
 2. A method as claimed inclaim 1, including:employing the second shield layer as a first polepiece layer; forming a write gap layer on the first pole piece layer;forming an insulation stack with one or more coil layers on the firstpole piece layer; and forming a second pole piece layer that isseparated by the write gap layer at the ABS, is connected to the firstpole piece layer at a back gap with the insulation stack beingsandwiched between the first and second pole piece layers at a locationbetween the ABS and the back gap.
 3. A method as claimed in claim 1,wherein the steps of removing the first and second portions, theadditional portion and the further first and second portions of the readsensor material layer is accomplished by forming first, second and thirdbi-layer photoresist masks respectively.
 4. A method as claimed in claim3, including:after forming the second mask removing said additional readsensor material layer through an opening in the mask exposing the firstgap layer; and depositing a refill insulation layer through the openingin the mask for the first gap layer to protect the first gap layer fromsubsequent processing.
 5. A method as claimed in claim 4, including:thesecond mask having first and second outside edges and the third maskhaving first and second openings wherein each of the first and secondopenings has first and second inside edges; and a location of the firstand second outside edges being spaced outboard of the first side edge ofthe first and second openings respectively with respect to the readsensor site to provide first and second spaces respectively wherein thefirst and second spaces occupy a portion of the first and second highresistance lead layer sites respectively; and each of said first andsecond spaces containing a portion of said refill insulation layer.
 6. Amethod as claimed in claim 5, including:after forming the third mask,milling through the first and second openings to remove the furtherfirst and second portions of the read sensor material layer as well assaid portion of the refill insulation layer within each of the first andsecond openings; and the portion of the refill insulation layer and theportion of the read sensor material layer in each of the first andsecond openings of the third mask being simultaneously completelyconsumed by said milling so that the first gap layer remains with auniform thickness in each of the first and second openings.
 7. A methodas claimed in claim 6, including:employing the second shield layer as afirst pole piece layer; forming a write gap layer on the first polepiece layer; forming an insulation stack with one or more coil layers onthe first pole piece layer; and forming a second pole piece layer thatis separated by the write gap layer at the ABS, is connected to thefirst pole piece layer at a back gap with the insulation stack beingsandwiched between the first and second pole piece layers at a locationbetween the ABS and the back gap.
 8. A method as claimed in claim 7,wherein each high resistance lead layer is made of Ta and each lowresistance lead layer is made of Au or Cu.
 9. A method as claimed inclaim 1, wherein a lateral width of each high resistance lead layeralong said ABS and a thickness thereof are chosen so as to minimize thethickness while optimizing an electrical resistance thereof.
 10. Amethod as claimed in claim 1, wherein each high resistance lead layerextends from a respective side edge of the read sensor in a directionperpendicular to the ABS to make electrical contact with a respectivelow resistance lead layer.
 11. A method as claimed in claim 10, whereina lateral width of each high resistance lead layer along said ABS and athickness thereof are chosen so as to minimize the thickness whileoptimizing an electrical resistance thereof.
 12. A method as claimed inclaim 11, including:employing the second shield layer as a first polepiece layer; forming a write gap layer on the first pole piece layer;forming an insulation stack with one or more coil layers on the firstpole piece layer; and forming a second pole piece layer that isseparated by the write gap layer at the ABS, is connected to the firstpole piece layer at a back gap with the insulation stack beingsandwiched between the first and second pole piece layers at a locationbetween the ABS and the back gap.
 13. A method as claimed in claim 12,wherein the steps of removing the first and second portions, theadditional portion and the further first and second portions of the readsensor material layer is accomplished by forming first, second and thirdbi-layer photoresist masks respectively.
 14. A method as claimed inclaim 13, including:after forming the second mask removing saidadditional read sensor material layer through an opening in the maskexposing the first gap layer; and depositing a refill insulation layerthrough the opening in the mask for the first gap layer to protect thefirst gap layer from subsequent processing.
 15. A method as claimed inclaim 14, including:the second mask having first and second outsideedges and the third mask having first and second openings wherein eachof the first and second openings has first and second inside edges; anda location of the first and second outside edges being spaced outboardof the first side edge of the first and second openings respectivelywith respect to the read sensor site to provide first and second spacesrespectively wherein the first and second spaces occupy a portion of thefirst and second high resistance lead layer sites respectively; and eachof said first and second spaces containing a portion of said refillinsulation layer.
 16. A method as claimed in claim 15, including:afterforming the third mask, milling through the first and second openings toremove the further first and second portions of the read sensor materiallayer as well as said portion of the refill insulation layer within eachof the first and second openings; and the portion of the refillinsulation layer and the portion of the read sensor material layer ineach of the first and second openings of the third mask beingsimultaneously completely consumed by said milling so that the first gaplayer remains with a uniform thickness in each of the first and secondopenings.
 17. A method as claimed in claim 16, wherein each highresistance lead layer is made of Ta and each low resistance lead layeris made of Au or Cu.